2F Carb Sight Glass Leaking/Hard Cold Starts (1 Viewer)

[Gretsch]

Wondering here how important it is that the carb sight glass be sealed well. My carb sight glass seems to leak fuel pretty good. During the cold months, it seems like fuel leaks out of the carb via this sight glass when the truck sits. When I go to start it in the morning, it takes about 5 minutes and many tries to try and get it to catch and start up. Wondering if this is due in part to the fact the fuel bowl is being emptied overnight through the leak in the sight glass. Once she warms up after getting it started she runs fine until the fuel leaks out again while the truck sits. This takes a long time to happen (6-7 plus hours). I did a quick experiment yesterday before starting it. I checked the sight glass before trying to start it and there was hardly any fuel I could see in it. I pumped the pedal 4 times, checked the sight glass, and could now see the sight glass on the outside (as well as inside the glass)wet with fuel. I finally kept pumping the pedal until I could see fuel at the half mark on the sight glass. I tried to start the truck but again it was taking many attempts to finally get it to fire up. So it seems as though fuel is leaking out of the sight glass overnight. Can this be my reason for it being hard to start in the mornings? I know that some fuel can evaporate overnight even in a non-leaky sight glass setup. Could a leaky sight glass cause some kind of vacuum leak at the carb making it hard to start? Would having no fuel in the fuel bowl in the carb show up as these sorts of symptoms? Where can I get a seal for the sight glass on my carb? Is there a replacement sight glass kit available somewhere or should I just get some gasket material and try and replace the gaskets on mine. As always, thanks to the forum for replies.

 

[klinetime574]

Sight glass is sealed with an o-ring. Pull off the two screws, metal plate, sight glass, and then you’re at the o-ring. Might be able to match it with one from a kit of some sort. Not sure of the size off the top of my head. Might be kind of tricky to remove the glass with the top cover on.

I know they come in carb kits though. @cruiseroutfit sells kits that I will try next time. Not too impressed with the Hygrade for a FJ60 carb.

 

[FishTacos]

You should be able to find an appropriate o-ring at any well stocked hardware store. Are you sure it is leaking and not just evaporating from residual heat in the engine compartment?

 

[Spike Strip]

If that o ring has deteriorated to the point it's leaking, possibly from etoh gas, prolly time for a rebuilt.

 

[Gretsch]

Are you sure it is leaking and not just evaporating from residual heat in the engine compartment?

I am sure its leaking but not sure its totally draining the fuel from the bowl. Its an admitted guess on my part. Could just be evaporating normally. But based on what I saw with my test, the glass was dry before I pumped the pedal, and wet with fuel after on the outside. So the glass is definitely leaking. As to if its causing the fuel bowl to totally empty or not I am not sure. I am assuming so based on the fact I see the outside of the glass wet after filling the carb with gas.

If that o ring has deteriorated to the point it's leaking, possibly from etoh gas, prolly time for a rebuilt.

Carb was rebuilt by the Cruiser Specialist down in Austin Texas just before I purchased the truck. The sight glass looks original to me and I don't know if it was touched or not as part of the rebuild. Prolly would not be a total waste of time to have one of the carb gurus on here rebuild it again. The truck runs great other than the hard starts though so dunno.

Incidentally, I pumped the pedal like 7 times this morning and she fired right up first try so don't know what the deal is. My theory is that the fuel leaks out overnight, and when trying to start the truck after sitting, the fuel pump pumps in enough gas such as to keep up with the slow leak at the sight glass and finally get the truck to start. Then the engine warms up and the sight glass seals up better to keep fuel in the bowl. I normally only do two to three pumps of the pedal before trying to start so maybe thats just not enough to keep up with the rate of leak. 7 pumps got enough in there to get the fuel needed to start the truck despite the leak.

Could a leaky sight glass cause a potential vacuum leak at the carb or am I totally off base here? Also to be clear the sight glass seal is an actual O-ring, and not a specialized gasket?

 

[NeverGiveUpYota]

I have one of those from a kit I didn’t swap out. I could measure it and luk the dimensions so you can head to an Ace.
Tmrw tho, I’m at work till 11.

 

[NeverGiveUpYota]

I am sure its leaking but not sure its totally draining the fuel from the bowl. Its an admitted guess on my part. Could just be evaporating normally. But based on what I saw with my test, the glass was dry before I pumped the pedal, and wet with fuel after on the outside. So the glass is definitely leaking. As to if its causing the fuel bowl to totally empty or not I am not sure. I am assuming so based on the fact I see the outside of the glass wet after filling the carb with gas.



Carb was rebuilt by the Cruiser Specialist down in Austin Texas just before I purchased the truck. The sight glass looks original to me and I don't know if it was touched or not as part of the rebuild. Prolly would not be a total waste of time to have one of the carb gurus on here rebuild it again. The truck runs great other than the hard starts though so dunno.

Incidentally, I pumped the pedal like 7 times this morning and she fired right up first try so don't know what the deal is. My theory is that the fuel leaks out overnight, and when trying to start the truck after sitting, the fuel pump pumps in enough gas such as to keep up with the slow leak at the sight glass and finally get the truck to start. Then the engine warms up and the sight glass seals up better to keep fuel in the bowl. I normally only do two to three pumps of the pedal before trying to start so maybe thats just not enough to keep up with the rate of leak. 7 pumps got enough in there to get the fuel needed to start the truck despite the leak.

Could a leaky sight glass cause a potential vacuum leak at the carb or am I totally off base here? Also to be clear the sight glass seal is an actual O-ring, and not a specialized gasket?

No. Vacuum leaks typically come from below the carb.

 

[NeverGiveUpYota]

Are you priming the carb before trying to start? Sounds like you had w/ the “7 times” so just keep doing that especially in colder weather.
Sorry for my consistent editing... I tend to read from bottom up.
Prime the carb in cold weather.fuel leaking out of the glass isn’t going to cause a hard start in my thinking... carbs are known to loose fuel over night. Very few of our 30+ year old carbs are that tight that they’ll hold all the fuel in the bowl from 6/8 hours previously. Plus you shut the truck off and it’s hot, the metal, etc. Fuel evaporates best when hot.

 

[Spike Strip]

RFG will evap much quicker than the gas that was available when your carb was designed. If the sight-glass is leaking coupled with the behavior of RFG when it sits for a few days, you're emptying the floatbowl and it's gonna take a bunch of cranks to fill it up before engine will fire.

I'm sure I've got a half-dozen of those O-rings. If you need one, PM me and I can mail it to you.

Be sure and use a JIS screwdriver on those small screws or you bugger 'em. I'd also squirt a few days with penetrant.

 

[FishTacos]

Also to be clear the sight glass seal is an actual O-ring, and not a specialized gasket?

Yes. It is just an o-ring. You should try to find one made of nitrile or otherwise listed as non-reactive with gasoline. Also, the sight glass is the same diameter and close to the same thickness as a nickel. I ran my truck with a nickel in its place for about a month one time when I had a cracked glass.

I know, I know....pretty shade tree....but it kept the gas in there.

Edit: or just take up spike on his nice offer.

 

[Spike Strip]

Not an LC carb but pretty much the same.

 

[Spike Strip]

Also, be careful when removing the glass, it's old and been through a million heat cycles so it chips easily. Don't pry it!

 

[Gretsch]

I have one of those from a kit I didn’t swap out. I could measure it and luk the dimensions so you can head to an Ace.
Tmrw tho, I’m at work till 11.

That would be outstanding Felicity. Thanks. I'll take whatever time you have. Thanks again.

fuel leaking out of the glass isn’t going to cause a hard start in my thinking... carbs are known to loose fuel over night. Very few of our 30+ year old carbs are that tight that they’ll hold all the fuel in the bowl from 6/8 hours previously. Plus you shut the truck off and it’s hot, the metal, etc. Fuel evaporates best when hot.

I may be barking up the wrong tree here with the hard starts. If fuel leaking out of the bowl wouldn't do this then I may just move on to something else. Its really cold weather that does this on my truck. And when I say cold, that's relative here in Texas. Anything below mid-40's seems to do this for me. I understand the evaporation of fuel is pretty common on these trucks, so again if what I am thinking sounds like horsesh!4, then I'll drop it and move on.

I'm sure I've got a half-dozen of those O-rings. If you need one, PM me and I can mail it to you.

Be sure and use a JIS screwdriver on those small screws or you bugger 'em. I'd also squirt a few days with penetrant.

Again outstanding. Appreciate the offer here @Spike Strip. I'll try and find one local and if not I'll reach out to you and take you up on it. Again if this won't help with my hard starts then I may just leave it for another battle elsewhere. Its leaks but not bad enough to really make it a problem.....unless its why I can get the thing started. I just thought if fuel was leaking out over night more quickly than simple evaporation because of the seal then maybe it would take a bunch of cranks to get fuel into the bowl to allow the truck to start. I'll prime it tomorrow again like today and see what I get. It was warmer here today than it has been for awhile so it could just have been that as to why it started up so quick. Also thanks for the JIS tip. Saved me from dicking these up.

Thanks all for the replies.

 

[2mbb]

I remember, some time ago, JimC (I think) said that fuel can't leak out of the bowl...at least not into the engine. You can see from the cutaway diagram that the discharge points inside the carburetor are all above the normal level of gas in the bowl. either vacuum or pressure (via the accelerator pump) is needed. That being said, if I do let my truck sit a few days, it does take some time and a lot of pumping to get it started.

If the site glass is leaking, the level will drop, but not to the level that will prevent the accelerator pump from working. Also, it shouldn't take many engine revolutions to "top off" the bowl. But you can also see there are two access plugs at the bottom of the bowl, so make sure these are not leaking, too. If these are leaking, they could completely drain your bowl.

Cold start of the 2F requires several pump of the accelerator pump (that is already primed with gas) and the choke pulled out--you don't mention anything about using the choke in your post. Make sure the choke plate is closing when you pull the knob.

 

[Gretsch]

I remember, some time ago, JimC (I think) said that fuel can't leak out of the bowl...at least not into the engine. You can see from the cutaway diagram that the discharge points inside the carburetor are all above the normal level of gas in the bowl. either vacuum or pressure (via the accelerator pump) is needed. That being said, if I do let my truck sit a few days, it does take some time and a lot of pumping to get it started.

If the site glass is leaking, the level will drop, but not to the level that will prevent the accelerator pump from working. Also, it shouldn't take many engine revolutions to "top off" the bowl. But you can also see there are two access plugs at the bottom of the bowl, so make sure these are not leaking, too. If these are leaking, they could completely drain your bowl.

Cold start of the 2F requires several pump of the accelerator pump (that is already primed with gas) and the choke pulled out--you don't mention anything about using the choke in your post. Make sure the choke plate is closing when you pull the knob.

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OK thanks for this. Yeah I can see where even if the sight glass was leaking it wouldn't drop down enough to drain it completely. I do typically use the choke to start it when cold which I failed to mention. Sounds like a sight glass leak is nothing to cause hard starts. One of the things that's been on my list for some time is to verify the choke plate operation. Choke seems to work properly but have never verified the plate operation. Thanks all for the help here.